Radioreceiver



Jan. 9, 1934. J. H. APPEL, JR

RADIORECEIVER Filed Jan. 12, 1932 2 Sheets-Sheet l i f-. /1 f u fw J9 Z SYM DAW-'5M /f if ATTORNEY Jan. 9, 1934. J. H. APPEL, JR

RADIORECEIVER Filed Jan. l2, 1932 2 Sheets-Sheet 2 yagww "f3 ATTORNEY Patented Jan. 9, 1934 UNITED STATES ENT OFFICE 2 Claims.

This invention relates to radio receivers and relates more particularly to a receiver adapted to receive both high and low broadcast frequencies.

In the United States of America, the radio transmitting stations which broadcast entertainment features operate at from 250 to 550 meters. The constants of the electrical circuits, such as values of inductances and capacities in broadcast receivers, are designed to operate most effectively at such wave lengths. Lately, however, there has been considerable interest and activity in the broadcasting of higher frequency or shorter Wave length signals, and at the present time, many broadcasting stations in foreign countries are broadcasting on shorter wave lengths or higher frequencies than in the broadcast band used in the United States. It is remarkable that under certain conditions greater distances are covered in the transmission of short wave or high frequencies than with what we know as the ordinary broadcast band. At the present time, a great deal of interest is being shown in the reception of short Wave radio bands, and, in order to enable the owner of a broadcast receiver to utilize his receiver in receiving the short Wave signals, what is known as short wave converters have appeared on the market which, when connected to an ordinary broadcast receiver, enable short wave and long wave signals to be received. The action of the most effective short wave converters, when used with a broadcast receiver is to receive the short wave signal, to generate a high frequency signal which beats by heterodyne action with the high frequencies of the short -wave signals, the heterodyne action converting the short wave or high frequency signal into a long wave or low frequency signal to which the standard broadcast receiver is tuned, the radio receiver portion of the standard broadcast receiver then vacting as an intermediate frequency amplifier in the well known superheterodyne action.

A fault of the short wave converters that have been developed is that the converter has had to be used as a complete separate unit having its own dial, for the selection of frequencies to which the set is to be tuned, and its own operating controls. The ordinary broadcast receiver, of course, has its own frequency selection dial and its own operating controls. In order to receive high frequency or short Wave signals with an ordinary set, the dial of an ordinary receiver is left at a selected point, thus tuning the set to a frequency, for example, of 600 kilocycles. The associated short wave converter then has its controls manipulated so as to simultaneously tune its input circuit to the short wave desired and to set in operation an oscillator which produces a frequency which heterodynes with the short Wave signal to produce a resultant signal having a frequency of the 600 kilocycles to which the broadcast receiver is tuned, this signal being amplified in the broadcast receiver and converted into sound waves through the associated loud speaker in the ordinary known manner. It is seen that with such a converter, not only is there necessary one or more dials for the operation of the standard broadcast receiver, but also one or more dials for the operation of the short wave converter. This multiplicity of controls is undesirable.

It not only complicates the operation of a. radio receiver, but the many controls are undesirable from the standpoint of appearance. While short wave converters have been supplied as separate units for association with broadcast receivers and have also been incorporated in the same cabinet with its associated broadcast receiver, the above remarks are applicable in both instances. There has always been the two separate sets of controls.

An object of this invention is to simplify the controls in a receiver for the reception of radio signals. Another object of this invention is to provide a frequency converter in combination with a radio receiver having a single frequency selecting dial.

A more definite object of the invention is to provide a radio receiving set Which receives short wave and standard broadcast Waves through the manipulation of a single tuning dial.

Another object of the invention is to provide a short wave converter having an output stage of amplification tuned to a frequency to which the standard broadcast receiver is automatically tuned when the short wave signals are being received.

In one embodiment of the invention, a short wave converter comprises input inductances which are tuned to the short wave signals to be received, a detector, an oscillator which is tuned to set up frequencies which heterodyne with the frequencies received in the short Wave band, and a tuned intermediate frequency amplifier which amplies the heterodyne signal and passes it at a constant frequency to the input circuit of an ordinary broadcast receiver. The broadcast receiver which is designed toco-operate with the short Wave converter comprises an ordinary receiver having several tuned radio frequency amplifier stages, a detector, audio-frequency ampliner, and loud speaker. A single tuning dial is em- Cil ployed for the manipulation o F the tuning condensers or the short wave converter and of the broadcast receiver, he shafts of the two sets of condensers being connected to the single dial. The shait connecting the dial to the condens-ers of the broadcast receiver is provided with a clutch arrangement which, when a separate control knob is manipulated, releases the shaft of the broadcast condensers from the dial, permitting the dial with the condensers of the short wave set to be rotated. The arrangement is such that the broadcast condensers, when released from the dial have their moi/'able plates always in mesh to the same degree with their plates, this resulting in the broadcast receiver always being tuned to a definite predetermined frequency when the clutch control is effecten. rotation of the dial with the broadcast condensers released then rotates the movable plates of the short wave converter which tune the converter to diiferent short waves or high frequencies. The condensers of the converter tune the input stage and csc' lator of the converter so that the frequencies received by the converter are heterodyned by frequencies generated by the oscillator to give a heterodyne signal at a frequency which is the particular frequency to which the standard broadcast receiver has been tuned by its variable condensers when the clutch on their` shaft has been released. When it is desired to receive ordinary broadcast frequencies, the clutch control is manipulated to permit the tuning dial to pick up the tuning condensers of the broadcast receiver at their proper relation with respect to the marking on the dial so that the condensers of the broadcast receiver are operated to tune the broadcast receiver to the desired frequencies. A separate control may be manipulated to transfer the receiving antenna from the short wave to the broadcast receiver input and vice versa.

A feature of the invention resides in not only that a single dial is used to indicate numerically or otherwise both standard and short wave frequencies, but by having the tuned stages of the broadcast receiver tuned always to the same frequency when the control clutch is operated, a tuned output stage tuned to that particular frequency may be and is combined as the output stage of the short wave converter. This results in the short wave converter delivering a signal of constant intermediate frequency to which the broadcast receiver is always tuned. This overcomes many disadvantages of the ordinary short wave converter since the many diiculties in coupling the output of a converter to the input of a broadcast receiver are done away with. Ordinarily, when a short wave converter is used with a broadcast receiver, the broadcast receiver is left tuned to no particular frequency, but to one depending upon the position to which its dial was last turned, and the controls of the converter are manipulated to deliver a heterodyne signal, to the standard receiver, which, of necessity, had to have a frequency equal to that to which the broadcast receiver last tuned. This meant that different heterodyne frequencies from the converter had to be delivered as the frequencies to which the broadcast receiver were tuned varied, this resulting in inaccurate logging of the received signals since at different times the broadcast receiver would be tuned to different frequencies with all of which the short wave converter had to co-operate- Another great fault of the ordinary converter arrangement is that the short Wave converter delivered diierent heterodyne frequencies to the input of the broadcast receiver, the circuit not being tuned to such frequencies, this resulting in a great loss of energy in the coupling of the converter to the receiver. According to this invention, however, the broadcast receiver is always tuned to a constant frequency when short waves are being received and 71e circuit including the output vof the converter and the input of the broadcast receiver is tuned to this particular frequency, this resulting, as is well known, in maximum transfer of energy and minimum loss. The invention will now be described with reference to the drawings, of which:

Fig. 1 is a partial front view of the tuning condensers of a broadcast receiver, tuning condensers of a short wave converter, a single dial for adjusting both sets of condensers, and a clutch mechanism for disengaging the broadcast condensers;

Fig. 2 is a sectional View along the lines 2 2 of Fig. 1;

Fig. 3 is a sectional View along the lines 3-3 of Fig. 1;

Fig. 4 is an enlarged projected View of the clutch actuating member of Fig. 1, and

5 is a circuit diagram of a standard broadcast receiver and a short wave converter adapted to co-operate with the mechanism of Figs. 1 to i inclusive.

The condenser assembly shown by Figs. 1 to 3 comprises an ordinary metal base 10, upon which is mounted the three broadcast tuning condensers l1, and the two short wave tuning condensers 12. A single dial 13, manipulated by the control knob 14, is provided with marked graduadicate the frequencies to which the rermed. The shaft 15 of the short wave condensers 12 is continuous and is permanently attached to the dial 13. The shaft 16 of the broadcast condensers 11 is connected to the shaft i7 of the dial 13 by means of a clutch made up of the two clutch members 13 and 19. The clutch member 18 is permanently attached to the condenser shaft 16 and the clutch member 19 is permanently attached to the dial shaft 17. The clutch member 19 is provided with the extension 2O and the clutch member 18 is provided with a recess 2l which is shaped to receive the extension 2G when the extension is in line with the recess and the associated clutch control operated. The mechanism for engaging the clutch members 18 and 19 comprises an eccentric member 22 which is attached to a control knob readily accessible to the operator of the receiver, a clutch member 23 (shown in more detail by Fig. 4), and which provided with the forked extensions 24 which nt in and cooperate with the recess 25 in the clutch member 18.

Grdinarily the clutch mechanism is not operated and the knob 13 and the condensers 11 are l so arranged that the 0 mark on the condenser when opposite a hair line on a transparent indicator (not shown) indicates that the movable plates of the condense-rs 11 are completely out of mesh with the result that the circuits tuned ly rneshed with the fixed plates and their cir- 'Y cuits tuned to maximum wave length or minimum frequency.

In the position shown by Figs. 1, 2 and 3, the

clutch mechanism has been operated by manipulation of the eccentric 22 which, in turn, moves the clutch member 23 to the left (facing the drawings and through the pressure of the forked extensions 24 on the clutch member 18, disengages the extension 20 from its associated recess 21, this enabling the shaft 17 to rotate freely within the clutch member 18 without any tendency to carry with it the clutch member 18 and its associated movable plates of the condensers 1l. The clutch member 23 is provided with the spring 26 which normally tends to keep the clutch mechanism in engagement.

The position of the extension 20 on the clutch member 19, and its associated opening 21 on the clutch member 18, are so placed with respect to the indications on the dial 13, and, of course, the position of the movable plates of the condensers 11 with respect to their fixed plates, that a predetermined frequency is tuned by the broadcast condensers 11 when the clutch mechanism is to be released. For example, 1000 kilocycles is the frequency which may be chosen as the frequency to which the radio frequency stages of the broadcast receiver are to act as intermediate frequency amplifiers for the heterodyne signal set up by the short wave converter. A red line, for example, is placed on the dial 13 at the position opposite the cross hair of the indicator when the condensers 11 tune the radio frequency stages of the broadcast receiver to 1000 kilocycles. This red line has been illustrated as a heavy line at the division 25 on Figs. 1 and 2 of the drawings.

In operation, referring now more particularly to Figs. 1, 2 and 5 of the drawings, where like symbols indicate like parts, when it is desired to receive broadcast frequencies, the switch 27 is placed on the contact 28. The condensers 11 are then tuned to a frequency corresponding to the broadcast signal desired. The apparatus shown generally by the symbol 30 at the upper part of Fig. 5, by the symbol 31 at the lower right hand side of Fig. 5, and by the symbol 32 at the lower left hand side of Fig. 5, are well known to those skilled in the art and will not be explained in detail. The portion of the apparatus shown by numeral 30 is, of course, a standard tuned amplier suitable for receiving broadcast signals. The apparatus shown generally by numeral 31 is a rectifier source for supplying the vacuum tubes with filament plate and biasing voltages. The apparatus shown generally by numeral 32 is a short wave converter, the operation of which will be explained in more detail later on in the specification.

When it is desired to receive short wave signals, the switch 27 is set at one orV the other terminals 33, 34 or 35 of the antenna coils of the short wave converter 32. The switch 36 which is a part of the short wave converter 32 is simultaneously set in contact with one of the terminals 37, 38, or 39 of the grid coils of the converter. The purpose of the several terminals 33, 34, and 35 and their associated terminals 37, 38, and 39 respectively are to enable the short Wave converter to be efficiently tuned to different bands of short wave frequencies. After the switches 27 and 36 have been simultaneously adjusted, the dial 13 is rotated until the heavy line at the symbol 25 is opposite the cross hair of the indicator, and the knob governing the position of the eccentric 22 is manipulated to cause the clutch member 23, to move the clutch member 18, away from the member 19, against the action of the spring 26, and disengage the extension 20 from its` associated recess 21. The position of the movable plates of the condensers 11, with respect to the fixed plates,

as has already been described, is such that the radio frequency stages of the broadcast receiver are tuned to 1000 kilocycles. The dial 13 is then rotated and moves only the movable plates of the short wave condensers 12 thus tuning the input and oscillator circuits of the short wave converter 32 to receive the high frequency signal, to generate the proper beating frequency, and to deliver the resultant heterodyne frequency of 1000 kilocycles to the broadcast receiver. `The markings on the dial 13, together with the position cf the switches 27 and 36, thus gives an indication of the wave length or frequency of the short wave signals being received.

When it is desired to again receive broadcast frequencies, the clutch is released and the dial 13 is rotated until the 100 division is opposite the cross hair of the indicator. During this rotation, the extension 17 of the clutch member 19 is brought, by the action of the spring 26 on the clutch member 23, into its associated recess 21 so that the condensers 11 are again positively engaged. Obviously, the condensers 11 can only be picked up by the clutch arrangement when their movable plates are in their proper relation to their fixed plates, as indicated by the markings on the dial with respect to the cross hair on the indicator. The switch arm 27 is shifted to the contact 28 and the dial 13 is now adjusted to tune the broadcast receiver to broadcast frequencies.

The short wave converter 32 is provided with an integral intermediate frequency amplifier stage which is tuned to 1000 cycles. This stage comprises the condenser 40, the inductance 41, and the thermionic amplifier` 42, the output which is connected to the input circuit of the broadcast receiver 30 through the capacity 43. The circuit, including the input circuit of the broadcast receiver 30, the coupling condenser 43, the output circuit of the vacuum tube 42, the condenser 40, the inductance 41, and their associated apparatus is so arranged that the complete circuit is tuned to 1000 cycles. The condenser 43 has been shown adjustable in order that any inequalities in the input circuit of the broadcast receiver 30 and the coupling wiring may be compensated for in order that the ent-ire circuit may be tuned to the intermediate frequency of 1000 cycles to which the circuit of the vacuum tube 42 and the radio frequency stages of the receiver 30 have been tuned. The converter 32 is, by this arrangement, enabled to deliver a heterodyne signal having a constant frequency to a broadcast receiver which is already tuned to this same frequency. This results, as has previously been explained, in the elimination of the coupling losses encountered in ordinary converter circuits and enables not only the single dial to tune a receiver to the two widely separated bands of frequencies, but to enable, through. the elimination of losses and the more advantageous circuit arrangement. a receiver highly sensitive to high frequencies to be obtained.

While the broadcast receiver 30 has been designed and operated to cover the ordinary broad- 1 I cast ranges. and the short wave converter 32 has been described as designed to transform high frequencies into low frequencies which are amplified into the broadcast receiver, it is obvious that, with this arrangement, rany two separated bands of .frequencies may be tuned through a. single dial, and this regardless of whether the frequencies are above or below the frequencies now generally designated as broadcast frequencies.

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Wiiile the circuit of the broadcast receiver 30 has been illustrated as of the ordinary tuned radio frequency type, it is obvious that any other type of receiver circuit, suitable for receiving broadcast receivers, could be utilized. Another type of receiver circuit which could be utilized is tiie superlieterodyne type which may also` lioWev-er, include tuned radio frequency stages ahead oi the first detector.

Whereas one or incre embodiments of the invention been described purposes of ilustration, should be understood that the invention is not limited to the particuiar embodiments d nrbed, but that suon embodiments of the invention are capable of modiication by, and other embodiments may be evolved by, those skilled in the art Without departing from the spirit of the invention.

What is claimed is:

l. in combination. a broadcast receiver, a snort Wave converter adapted to deliver a constant lieterodyne signal to receiver, a geng of variabe condenscrs for tuning the selective circuits of receiver, another gang ci con.- densers for tuning the selective oscillator circuits of said converter, a single dial for op erating bot-ii of 'd gangs of condensers, an in dicator for indica.y iig when said first mentioned gang of condensers has tui. d the selective circuits of broadcast eceiver t the lieterodyne signal delivered by said converter, and means for disconnecting said iirst mentioned gang of condensers from said dial, whereupon the dial may then be used to adjust only the gang of condensers associated with the short Wave converter.

2. in combination, a broadcast receiver, a high frequency converter having a selective circuit tunable to, and a detector for, detecting the high frequencies to be received, an oscillator which generates currents which beat with the received nigh frequencies to generate a heterodyne signal which is supplied to said broadcast receiver, an oscillator circuit determining the frequency at viiicii said oscillator oscillates, a gang of condens-ers for tuning the selective and oscillator' circuits said converter, another gang of variable condesers for tuning ne selective circuits of said broadcast receiver, a single dial for o erating simultaneously both gangs of condens-ers, means for disconnecting said second mentioned gang condensers when it is desired te receive the liiefli frequency signals, designations on diai to indicate the settings of the condense s an indicator, and a separate means associ JOSEPH H. APPEL, JR. 

